Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 143372

143372 - Modeling of Ultra-Fast Micro-Actuation Using Thermal Bubble-Driven Micro-Pumps 

Thermal bubble-driven micro-pumps (also known as inertial micro-pumps) are an upcoming micro-actuation technology for moving fluid without the use of external pump sources. These micro-pumps are essentially high-power thermal inkjet resistors. A current pulse heats the surface of the resistor to 300 °C in microseconds causing explosive boiling of an interfacial fluid layer which forms a high pressure (10’s atm) vapor bubble. This vapor bubble is then harnessed to perform mechanical work. Historically, thermal bubble-driven micro-pumps have been demonstrated for fluidic operations such as pumping, mixing, routing/sorting, and cell lysis. In this work, we extend the use of thermal bubble-driven micro-pumps to ultra-fast micro-actuation for use as a micro-robotic actuator.

 

Taking inspiration from the Mantis shrimp, we seek to develop a new class of micro-actuators for micro-robots that are both (a) ultra-fast and (b) high force. To date, these two criteria are difficult to achieve in micro-robotic actuators but have applications in both legged and winged micro-robots. The physics of thermal bubble-driven micro-pumps is well suited to satisfy both being an ultra-fast and high force micro-actuator since the high-pressure vapor bubble has a lifetime of less than 30 us and has an internal pressure of 10’s atm. In this study, micro-channels with a cross-section of 500 x 50 um² are fabricated using a femtosecond laser cutter and are sealed with a thin membrane (Mylar and PVDF films). The micro-channels are aligned and placed over a high-power thermal inkjet resistor that is laser cut from a sheet of ITO/FTO coated glass. Lastly, the micro-channels are filled with water. When the high-power resistor is actuated, the high-pressure vapor bubble causes the thin membrane to deflect. This fluid-structure interaction is complex due to the speed of actuation as well as its micro-scale size. In past work, we have performed experimental stroboscopic imaging and laser to probe the transient membrane deflection during actuation. Yet, a detailed analysis of fluid and membrane dynamics is not possible through experimental methodologies. As such, we develop numerical fluid-structure interaction (FSI) simulations using OpenFOAM and preCICE to analyze fluid, bubble, and membrane physics otherwise unable to study through experimental means. In general, we envision thermal bubble-driven micro-pumps as a viable means to enable ultra-fast micro-actuation for micro-robotics.

Presenting Author: Brandon Hayes University of Colorado Boulder

Presenting Author Biography: Brandon is a PhD candidate at the University of Colorado Boulder in Mechanical Engineering. His research focuses on theoretical, experimental, and numerical investigation of thermal micro-bubbles for applications in robotics and microfluidics.

Authors:

Brandon Hayes University of Colorado Boulder
Robert Maccurdy University of Colorado Boulder